Field of the Invention
The present invention relates to an inkjet printing apparatus and a recovery method of a print head used in the inkjet printing apparatus.
Description of the Related Art
In an inkjet printing apparatus, ink supplied to a print head is injected on a print medium from ejection ports to print an image thereon. A cap is put on the ejection port of the print head, and a suction recovery process for performing suction through the cap is executed. This suction recovery process is executed for preventing or eliminating an ejection failure caused by ink thickened in viscosity, clogging of the ejection port due to adhesion of ink, air bubbles or foreign particles generated in a liquid passage communicated with the ejection port, and the like. At the time of starting with printing, this kind of suction recovery process is executed before the printing, and therefore the time required for completion of the printing becomes longer, resulting in making a user wait for the output.
On the other hand, Japanese Patent Laid-Open No. H02-092548 (1990) discloses a technology in which the suction recovery is executed according to an elapsed time from the previous printing. Therefore the recovery operation is performed only in a case where the suction aiming at removing the ink having adhered to the ejection port is necessary. That is, in a case where the printing is frequently performed, the suction recovery is not executed, and a user does not keep waiting for the output long.
In addition, Japanese Patent Laid-Open No. H06-166184 (1994) discloses a technology in which an elapsed time from the previous recovery process is calculated and a recovery process having a suction amount differing depending upon the elapsed time is executed. This technology thus prevents occurrence of the print failure even in a case where the apparatus is left in a non-use state for a long period of time while suppressing consumption of ink by suction at the recovery process.
However, in the sequence of the apparatus disclosed in Japanese Patent Laid-Open No. H02-092548 (1990), since the suction recovery is executed based upon the predetermined elapsed time from the previous printing, the suction is not executed in a case where the printing is frequently performed. In this process, the ink thickened in viscosity does not stay in the ejection port as long as the ejection continues to be performed, but air bubbles are possibly generated in the flow passage. Therefore in a case where the printing is frequently performed, the suction is not performed, and therefore it is not possible to prevent the ejection failure due to the air bubble mixed into the flow passage.
In addition, in the sequence of the apparatus disclosed in Japanese Patent Laid-Open No. H06-166184 (1994), the recovery process is executed based upon the elapsed time from the previous recovery process. Accordingly, in a case where a predetermined time elapses after the previous recovery process and the printing is frequently performed during the predetermined time, since the elapsed time from the previous printing is short, there is a little possibility that the adhesion of ink to the ejection port and the thicker viscosity of ink are generated. However, since the recovery process is executed according to a length of time from the previous recovery process, in some cases unnecessary recovery processes including a recovery operation for removing the ink having adhered to or thickened in viscosity in the ejection port are executed.